This invention relates to a removable blow head plate or gassing head plate for an automatic core machine sand blow head or gassing head or both, which machine is used to mold sand cores used in foundry casting of metal.
Conventional foundry casting generally comprises forming either a temporary sand mold or a permanent metal mold with one or more cavities into which molten metal is poured. The metal solidifies within the cavity and is removed to form a cast article. Where the article is hollowed or provided with openings, it is conventional to use a core which is arranged within the cavity so that the molten metal poured into the cavity solidifies around the core. Then, the core is broken and removed to leave the opening or hollow area within the article.
In general, the cores are formed by using shell core or hot box or cold box (utilizing gas) techniques. For example, in shell core or hot box core forming techniques, sand which is pre-coated with a binder of wax or resin or the like material, is dropped into the cavity in a core box mold for molding the sand into the shape of the desired core. The binder may be activated by using a self activating binder and catalyst mixture, which activates at room temperature, or by heating the core box to activate a binder mixture.
Where the cold box technique is used, a conventional gas, such as CO.sub.2, is blown into the mixture of sand and binder in the cavity to cause a chemical reaction which solidifies the sand and binder to form the solid molded core shape. Some variations of these techniques are utilized, in general, to cause the binder to activate either within a pre-determined time period.
Automatic machinery is utilized to rapidly form cores within cavities in core boxes, utilizing one or another of the above types of core forming techniques. These automatic machines typically include a sand hopper which stores sand and feeds the sand downwardly as required. A blow head is located beneath the hopper, essentially a container or box-like frame, that receives a charge of sand from the reservoir of sand. Sand is dropped downwardly through openings in a closure plate secured to the bottom of the blow head frame. The sand passing openings are aligned with corresponding portions of the core mold cavity in the core box located beneath the blow head.
Where a cold box or gassing technique is utilized, the machine may also have a gas storage container which feeds gas into a gassing head which is constructed similarly to the blow head and has a similar closure plate fastened to the bottom of the gassing box-like frame. The gas passes through openings in the gassing head closure plate and downwardly into a sand filled cavity in the core box located beneath the head.
Where the gassing technique is utilized, the automatic machine is provided with a mechanism for, first, locating a core box beneath the blow head for filling with sand and, then, for moving the core box beneath the gassing head for applying the gas for reacting the binder and setting the sand-binder mixture into the desired core shape. Where the hot box or shell technique is utilized, that is, where the binder is either set by a time related reaction or by the application of heat, the automatic machine may have only a blow head beneath which one or more core boxes may be positioned.
In the foregoing types of automatic core forming machines, the openings in the blow head or gassing head plates tend to become partially or fully plugged by accumulating solidified sand-binder material and, sometimes, the sand above and around the upper portions of the openings in the plate tends to crust or solidify. This occurs because, in the case of a heat setting binder, the heat rises and causes a reaction in the sand-binder mixture located above and around the openings during the times that the core sand-binder material is setting within the core cavity. In the case of the gassing heads, sometimes the sand binder material in the core raises or spills upwardly sufficiently to accumulate material in and around the plate openings to partially or fully plug them.
It can be seen, that over a period of time, the partial or full plugging of the openings in the plates adversely effect the filling of the core cavities and the proper setting of the core-binder mixtures in the core cavities. Hence, when that occurs, in conventional equipment, the automatic machine must be shut down and cooled. Then, the blow head or the gassing head or both must be manually removed from the machine. The lower plates, which are secured as closures, upon the frames must be cleaned and, then, the heads replaced. Where a different hole or opening pattern is needed for use with changed cavity arrangements within the core box, the plates must be unfastened from their frames and replaced. Typically, fastening involves the use of screws or similar types of mechanical fastening means which take considerable time for releasing and then reapplication for plate substitution. The replacement of the plates requires that the heads be cooled enough for manual contact.
Thus, the invention of this application is concerned with providing an assembly by which the closure plates, referred to as blow plates or gassing plates, of the blow head or gassing head of an automatic core forming machine may be replaced rapidly, without shutting down the machine more than short period of time, and without the necessity of cooling the machine. Hence, the plates can be replaced often to ensure that the opening are not obstructed or plugged.